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; ----- A Program to display ASCII characters -----------------
; ----- Here it is tidied up. This version is annotated. ------
; ----- This makes it possible to understand. -----------------
; ----- The labels have been given more readable names too. ---
Start:
Mov BL,C0 ; Make BL point to video RAM
Mov AL,3C ; 3C is the ASCII code of the 'less than' symbol
Here:
Mov [BL],AL ; Copy the ASCII code in AL to the RAM location that BL is pointing to.
CMP AL,7B ; Compare AL with '{'
JZ Clear ; If AL contained '{' jump to Clear:
INC AL ; Put the next ASCII code into AL
INC BL ; Make BL point to the next video RAM location
JMP Here ; Jump back to Here
Clear:
MOV CL,40 ; We are going to repeat 40 (hex) times
MOV AL,20 ; The ASCII code of the space character
MOV BL,C0 ; The address of the start of video RAM
Loop:
MOV [BL],AL ; Copy the ASCII space in AL to the video RAM that BL is pointing to.
INC BL ; Make BL point to the next video RAM location
DEC CL ; CL is counting down towards zero
JNZ Loop ; If CL is not zero jump back to Loop
JMP Start ; CL was zero so jump back to the Start and do it all again.
END
; -------------------------------------------------------------
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